Antenna coupling



' Aug. 13, 1946.

07472: ll/Tf/ 1417757054 W. SILVER ANTENNA COUPLING Filed July '7, 1943NVENTOR.

WALTER SILVE R Patented Aug. 13, 1946 UNITED STATES PATENT OFFICE(Granted under the act of March 3, ,1883, as amended April 30, 1928,;370 0. .G. 757) 7 Claims.

1 The invention described herein maybe manuiactured and used by or for.the Government for governmental purposes, without the payment to e ofany royalty thereon.

This invention relates to transmission line couplings and moreparticularly to couplings used between movable and stationary portionsof a line.

An object of the invention is to provide a coupling unit which willpermit a maximum transfer of energy between the separate components ofthe line.

Another object is to provide a coupling unit which will require aminimum of mechanical or electrical adjustment.

Still another object is to provide a coupling which will permit themaintenance of alow, substantially constant, standing wave ratio on thelines for all relative positions of the coupling unit.

According to the present invention the foregoing objects ar realized byproviding a coupling unit which is, in efiect, a pair of pretunedresonant circuits each comprising a coil and a capacitor associatedtherewith. The reactance and the capacitance of each portion of the unitare so chosen that said portions are resonant at a predeterminedfrequency and thus yield a 1:1 transformation. Such a 1:1transformation, of course, leaves untuned lines attached theretounaffected. Therefore, the insertion of such a unit at any point in aline from a transmitter or/and a receiver to an antenna does not upsetthe line characteristics.

For a better understanding of the invention, together with other andfurther objects thereof, reference is had to the following description,taken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

In the accompanying drawing the single figure is a perspective view ofmy coupling unit.

Referring now more particularly to the draw ing, the coupling unit Icomprises a rotatable coil 3 and a stationary coil 5 disposed invertical spaced parallel relation coaxially about a rigid, stationaryshaft 1. While in the interest of clarity, the coils are shown widelyseparated from each other, it will be understood that in the normaloperation of the unit the coils are positioned close to each other.

As shown, the rotatable coil 3 is a single turn of flat stock woundedgewise to provide a circular loop the ends of which are bent upwardlyat right angles to the plane of the loop to form spaced parallel platesl I, 13 with an air gap 9 therebetween. The combination of the pair ofplates and the air separation acts as a condenser G1 which, with thecoil 3, forms a tuned resonant LC circuit. If a condenser of greatercapacitance is desired, the area of the plates II and I 3 may beincreased. In the illustrated embodiment, the plates have been madewider than the coil. Connection to the LC circuit is made by means ofterminal blocks 15, I! carried on the outer surfaces of the plates ll,i3 near the free ends thereof. The blocks I5, I! are provided withsuitable apertures and fastening means to receive the transmission linesI9, 21 which connect to a rotatable antenna (not shown) In order .toprotect it from any adverse weather conditions, the coupling unit may beenclosed in a boxlike structure or housing H, which may be mounted on aturntable T for rotation with the antenna and the transmission lines [9,2! leading therefrom. When so enclosed, the coil 3 may be suspended fromthe top of the housing by means of a plurality of vertical insulatorsupport rods 23 which may be attached at one end to the coil and at theother to the housing, as shown.

"The stationary coil 5 and associated air condenser C2 are similar tothe above-described coil 3 and its associated condenser C1. Thisresonant LC circuit is mounted on and centered about the shaft 1 bymeans of a spider having arms 25 and extending radially from a hub 2!which is rigidly fixed to shaft 1 in any convenient manner. Verticalinsulator rods 23 are attached at their upper ends to the coil 5 and attheir lower ends to spider arms 25. The transmission lines 3|, 33

from the transmitter or/and the receiver (not shown) are connected tothe condenser C2 in the same manner in which, the antenna transmissionlines are connected to the condenser C1. It is to be noted that, if theabove-mentioned housing is used, an opening 34 concentric with shaft 1should be provided in the bottom wall of the housing through which thetransmission lines 3| 33 and the shaft 1 may pass. This opening permitsrotation of the housing H, the first described LC circuit 3 and C1, andthe attached antenna transmission lines I 9, 2|, while the shaft 1, theLC circuit 5 and C2 attached thereto. and the transmitter or/and thereceiver transmission lines 3! 33 remain stationary.

I have found that it is desirable to provide a disc 36 of insulatingmaterial, such as polystyrene or the like, of a diameter slightlysmaller than the opening 34 for the opening 34. As shown, the disc 36 iscoaxially attached to the shaft 1 in any convenient manner and isprovided with openings through which the transmission lines 3!, 33 maybe passed. The disc 36 serves both as a spacer for the lines and as aclosure member of the opening preventing dust, snow or other elementsfrom blowing into the housing H.

Suitable openings in the top of the housing H are provided to permit theshaft l and the transmission lines [9, 2i to extend therethrough.

A Faraday screen 35, comprising a plurality of straight uniform lengthsof wire 3i extending radially from a collar 39, is rigidly mounted onthe shaft 1 between the rotatable coil 3 and the stationary coil 5. Thepurpose of the screen is to prevent capacitative coupling between thecoils 3 and 5.

Capacitative coupling between the coils cannot be tolerated because, ifpresent, it would not be constant in magnitude, but would vary with therelative positions of the gaps 9 in the coils 3 and during relativerotation, and this variation would result in a change of input impedancefor a given fixed output impedance. In particular, there would be markedchange in coupling when the gaps periodically become vertically aligned.

The installation thus far described is one in which the antenna is largeand bulky, necessitating its mounting on a turntable using a circulartrack with rollers. However, a small light-weight antenna may besupported and rotated directly by a shaft. When used under suchcircumstances, it is merely necessary to invert the structure described.Thus viewing the figure in inverted position, it will be apparent thatunder these conditions, the spider supported LC circuit, composed of thecoil 5 and the condenser 02, would be connected to the antenna lines Si,33 and be rotatable therewith while the circuit, consisting of the coil3 and the condenser C1, would then be the stationary one and would beconnected to the transmitter or/and receiver by means of thetransmission lines ill, therefrom.

As pointed out above, in the norma1 operation of the unit, the coils 3,5 are brought much nearer to each other than is evident from theexploded view shown in the figure. For example, in one embodiment of thedevice the spacing of the coils was about /2 of the diameter of thecoils.

While there has been described what is at pres ent considered thepreferred embodiment of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall Within the true spirit and scope of the invention.

What is claimed is:

1. An electromagnetic device for coupling a rotatable antennatransmission line to a stationary antenna transmission line said devicecomprising a first tuned circuit connected to said rotatabletransmission line and a second tuned circuit connected to saidstationary transmission line, said first and second tuned circuitsincluding substantially circular inductance loops, said loops having 1transmission line and a second tuned LC circuit connected to saidstationary transmission line, each of said tuned circuits comprising asubstantially circular loop having a pair of free ends and an aircondenser connected to the free ends of said loop.

3. In an antenna transmission line having a stationary portion and arotatable portion, said stationary portion being connected to a radioapparatus, said rotatable portion being connected to an antenna, a shaftfixedly attached to said radio apparatus and disposed in parallelrelation to said stationary portion and said rotatable portion, a firstloop connected to said shaft and coaxially disposed thereto, said firstloop having a pair of free ends bent at right angles to the plane of theloop to form spaced parallel plates of a first air condenser, means onsaid plates for connecting said stationary portion thereto, a secondloop connected to said antenna and coaxially disposed to said shaft,said second loop having a pair of free ends bent at right angles to theplane of said second loop to form spaced parallel plates of a second aircondenser and means on said plates for connecting said rotatable portionthereto.

4:. In an antenna transmission line having a stationary portion and arotatable portion, said stationary portion being connected to a radioapparatus, said rotatable portion being connected to an antenna, a shaftfixedly attached to said radio apparatus and disposed in parallelrelation to said stationary portion and said rotatable portion, a firstsubstantially circular loop connected to said shaft and coaxiallydisposed thereto, said first loop having a pair of free ends bent atright angles to the plane of the loop to form spaced parallel plates ofa first air condenser, said first air condenser forming with said firstloop a tuned resonant circuit, means on said plates for connecting saidstationary portion thereto, a second substantially circular p connectedto said antenna and coaxially disposed to said shaft, said second loophaving a pair of free ends bent at right angles to the plane of saidloop to form spaced parallel plates of a second air condenser, saidsecond air condenser forming with said second loop a tuned resonantcircuit, and means on said plates for connecting said rotatable portionthereto.

5. In an antenna transmission line having a stationary portion and arotatable portion, said stationary portion being connected to a radioapparatus, said rotatable portion being connected to an antenna, a shaftfixedly attached to said radio apparatus and disposed in parallelrelation to said stationary portion and said rotatable portion, a firstsubstantially circular loop connected to said shaft and coaxiallydisposed thereto, said first loop having a pair of free ends bent atright angles to the plane of the loop to form spaced parallel plates ofa first air condenser, said first air condenser forming with said firstloop a tuned resonant circuit, means on said plates for connecting saidstationary portion thereto, a second substantially circular loopconnected to said antenna and coaxially disposed to said shaft, saidsecond 100p having a pair of free ends bent at right angles to the planeof said second loop to form spaced parallel plates of a second aircondenser, said second air condenser forming with said second loop atuned resonant circuit, means on said plates for connecting saidrotatable portion thereto, and means carried by said shaft andpositioned between said first and said second loops for eliminatingcapacitive coupling between said first and second loops.

6. A rotatable coupling unit adapted to couple a continuously rotatableantenna to a stationary transmission line, comprising a pair ofcoaxiallymounted, relatively-rotatable supports, one support being fixedand the other support being adapted to be continuously rotatable withsaid antenna, a pair of single-turn loops located in parallel planes,one of said loops being mounted on said fixed support and adapted to beconnected to said transmission line, and the other of said loops beingmounted on said rotatable support and adapted to be connected to saidantenna.

7. A rotatable coupling unit adapted to couple a continuously rotatableantenna to a stationary transmission line, comprising a, pair ofcoaxially mounted relatively rotatable supports, one support being fixedand the other support being adapted to be continuously rotatab1e withsaid antenna, a pair of identical, single-turn loops located in parallelplanes, one of said loops being mounted on said fixed support andadapted to be connected to said transmission line, and the other of saidloops being mounted on said rotatable support and adapted to beconnected to said antenna, adjacent ends of each loop being bent fromthe planes thereof to form a resonating capacity therefor, and anelectrostatic shield between said loops.

WALTER SILVER.

